1. Field of the Invention
The present invention relates to a curable composition.
2. Discussion of Related Art
High-brightness products have been obtained by using GaN compound semiconductors such as GaN, GaAlN, InGaN or InAlGaN as a light emitting diode (LED), for example, a blue or ultraviolet (UV) LED. Further, it becomes possible to form high-quality full color image by combining red and green LEDs with the blue LED. For example, a white LED prepared by using the blue or UV LED with phosphors is known. Demands of such LEDs has increased in the application of a backlight of a liquid crystal display (LCD) or a general light.
As an encapsulating material for an LED, an epoxy resin having a high adhesive property and excellent dynamic durability has been widely used. However, the epoxy resin has problems of low transmissivity with respect to light in a blue-to-UV region and low light resistance. Accordingly, for example, in the patent documents 1 to 3, techniques to improve such problems are suggested. However, encapsulating materials disclosed in the patent documents do not have sufficient light resistance.
As a material with excellent resistance to light having low wavelengths, a silicon resin is known. However, the silicon resin has low thermal resistance and tackness on a surface thereof after curing. Further, in order for the silicon resin to effectively function as the encapsulating material of the LED, it is necessary to ensure characteristics of high refraction, crack resistance, surface hardness, adhesive strength and thermal shock resistance.